Electric switch



May 3 1933- G. A. BURNHAM ELECTRIC SWITCH Filed July 13, 1931 ITTUB]? 702 1 W atented May 30, 1933 UNITED STATES PATENT OFFICE GEORGE A. BURNHAM, OF SAUGUS, IvIASSACTiUSETTS, ASSIGNOR T CONDIT ELECTRICAL MANUFACTURING CORPORATION, OF HYDE PARK, MASSACHUSETTS, A CORPORA- TION OF MASSACHUSETTS ELECTRIC SWITCH Application filed July 13,

This invention relates to electric switches and has for an object the improved manner of extinguishing the circuit lnterrupting are.

It has been proposed heretofore to utilize the gaseous pressure generated by the circuit interrupting are drawn in oil or other arc extinguishing liquid to force a stream of oil into intimate contact with the arm for the purpose of extinguishing it. In some 1nstances the pressure is generated by one are and the liquid is directed upon a second arc that is in series with the first arc. The methods heretofore employed, however, have been open to the objection that the pressure gases have commingled with the liquid stream so that the stream has not been as effective as has been intended, the stream being intermittent in action and variable in direction.

It is an object of the present invention to set in motion a stream of liquid by the pressure of gases formed by a circuit interrupting arc and to direct the stream against either another portion of thesame are or against a second arc in series with the first arc and to arrange the apparatus so that the liquid-forcing gases are kept out of the liquid stream at least until the circuit has been interrupted so that the liquid stream can be used with full effect in extinguishing the arc.

A further object of the invention is the provision of an electric switch arranged to draw a plurality of circuit interrupting arcs in series and to utilize the pressure of gas generated by one are in forclng a body of liquid such as oil against a second are that is in series with the first arc.

A further object of the invention is the provision of an electric switch having an oil reservoir provided with an outlet opening that is directed into the zone of a circuit interrupting arc and a chamber in which'an arc is drawn and in which pressure is built up to force the fluid from the reservoir free from pressure gases into the arc zone.

Another object of the invention is to direct oil or the equivalent, that is placed under pressure by the high pressure portion of an arc, into a low pressure portion of the arc, thereby having such a positive oil pres- 1931. Serial No. 550,380.

sure that the discharged oil can be directed as desired into the low pressure portion of the arc.

A further object is generally to improve the construction and operation of electric switches.

Fig. 1 is a side elevation of the components of a two-break electric oil switch arranged in accordance with the present invention.

Fig. 2 is a section along line 22 of Fig. 1.

Fig. 3 is a diagrammatic view of an electric switch and illustrating certain principles of the invention.

Fig. 4 is a sectional elevation through one pole of a switch having in modified form the principles of the invention.

Fig. 3 illustrates diagrammatically the principle of the invention. The switch comprises the insulated stationary contact member located in the upper end of an enclosing and oil-containing pressure-generating chamber 12. The movable contact member 14 is movablethrough an opening 16 in the bottom of the chamber into and out of engagement with the stationary contact member. In switch-open position the movable contact member is disposed somewhere below the bottom or" the pressure-generating chamber. The contact members and the pressure-generating chamber are submerged in oil or other equivalent arc-extinguishing liquid so that the chamber, under normal conditions, is filled with oil. An oil reservoir 18 is conveniently located with respect to the pres sure-generating chamber and is in communication therewith through the conduit 20. The reservoir 18 has an outlet conduit or nozzle 22 which extends from the bottom of the reservoir to a locationbeneath the bottom of the pressure-generating chamber 12 and above the movable contact member 14 when the latter is in switch-open position so that the contents of the reservoir 18 can be discharged into intimate contact with the are that is formed between the contact members and passes through the opening 16 during circuit interruption. The reservoir 18 is also submerged beneath the level of oil in the enclosing casing, not shown, of the switch so that under normal conditions the reservoir is completely filled with oil. The reservoir is provided with a small vent 24 and the pressuL'e-generating chamber 12 is also provided with a small vent 26 so that gases present in said reservoir and chamber during circuit interruption subsequently can escape and allow the reservoir and chamber to be refilled with oil prior to and following the opening operation of the switch. The operation of the switch is essentially as follows:

When the switch is opened under load the contacts 10 and 14 are separated and a circuit inteirupting arc is drawn between them and in the confined body of oil in the pressuregenerati 1g chamber 12. Some of the oil is v porized and gasified and a substantial gas pre ure is created within the chamber. This pre. are is transmitted through the conduit 10 to the oil reservoir 18, the pressure gases and also some of the oil under pressure in the chamber 12 flowing into the'oil reservoir 18. The oil in said reservoir is consequently placed under pressure and thus is forced through the discharge passage 22. The movable contact member 1 L during switchopening movement moves out of the opening 153 of the chamber 12 and draws the are out of the chamber where the arc encounters the stream of oil flowing from the outlet passage 22 of the oil reservoir and thus becomes cool and extinguished, so that the circuit is interrupted. The pressure generating chamber 12 is intended to be such that a relatively high seous pressure is generated and maintained therein and in the oil reservoir 18 until the circuit has been extinguished at the outside of the chamber. The oil reservoir 18 is intended to contain a volume of oil sufficient to cifect the extinguishing of the are outside of the chamber before the reservoir is emptied of oil. Since the contact member 1+1. is intended to be withdrawn from the chamber 12 at relatively high speed, the liquid capacity of the oil reservoir 18 need not be great.

Fig. 1 illustrates the application of the principle of Fig. 3 to a two-breali electric switch. In this modification the stationary contact members and 32 are carried at the lower ends of the switch terminals 34 and 36 and are located in the upper ends of pressuregenerating chambers 38 and L0 which are submerged in the body of oil contained in the enclosing casing, not shown, of the switch. The movable contact members 42 and ii are carried by the bridging member 46 which is raised and lowered by a lifting rod i8 operated by suitable mechanism not herein shown. The movable contact members pass upwardly and through openings 50 and 52 of the pressuregenerating chambers and engage the stationary contact members 30 and 32 there in to complete the circuit through the switch. In the switch-open position the movable contact members are out of and below the pressure-generating chambers and when the switch is opened under load, the movable contact members are adapted. to draw circuit-interrupting arcs through the openings of the chambers. The chamber 38 is provided with a conduit at of insulating material, or composed at least in part of insulating material. Said conduit is in communication with the interior of the chamber 38 at the bottom and at one side thereof and extends to a location immediately under the other chamber where its opening is in a position to discharge oil into the zone of the are at and beiow the opening 52 of said chamber 4:0. The chamber 10 is provided with a similar conduit 56 which extends to the chamber 38 and is similarly disposed to direct a stream of fluid into the are drawn out of the opening in said chamber.

The operation of this modification is essentially as follows:

hen the switch is opened under load, the movable contacts i2 and i i are withdrawn from engagement with the stationary contacts and arcs are drawn between the contacts in the bodies of oil contained in the chambers 38 and i0. under substantial pressure are generated from the bodies of oil thereby forcing the bodies of oil contained in the condr'ts 5st and 56 into the Zones of the arcs drawn through the openings and 52 of the c mbers when the movable contact mem s emerge from said chambers and thereby cooling and extinguishing the arcs. Oil from said chambers 38 and 4.0 also flows therefrom into the conduits 5-iand 56. The conduits are in con'nnunication with the chambers at the bottoms thereof and at the sides thereof so that the entrances to the conduits are relatively remote from the gas bubbles lorated between the stationary and movable contact members. Thus when oil from the chambers flows through the conduits 5% and 56 and is discharged into the arc zones under the chambers during the time that circuit-interrupting arcs are present outside the chambers, the amount of gas-free oil that is discharged from the conduits 5i and 50 and from the chambers into said conduits is intended to be suiiicient to exti guish the circiut interrupting arcs before the conduits become exhausted of oil. Each conduit and its pressure-generating chamber is thus the equivalent of the reservoir and the pressure-gem crating chamber of F 3 and the conduit can contain a substantn amount and ordinarily all of the oil that may be needed to extinguish the arc. After the arcs have been extinguished the gases in the chambers can escape through the v it openi: and 60 so that the chambers can be refilled with oil prior to the next circilit-interrupting operation of the switch.

Fig. 4 illustrates a further modified form of the invention. In this construction a cylindrical shell 62 has amovable piston 64 therein which divides the shell into two compartments, the upper compartment 66 comprising the pressure-generating chamber, and a lower compartment 68. An oil reservoir 70 surrounds the shell 62 and the upper and lower compartments 66 and 68 thereof and is open at the top into the pressure-generating chamber through the ports 7 2. The lower chamber 68 has an opening 74 in the bottom wall thereof and the oil reservoir 70 has an opening 7 6 in the bottom wall axially aligned with the aforesaid opening 7 4. The

space between the bottom walls of the shell 62 and the oil reservoir 70 provides a completely annular passage 78 through which the oil in the oil reservoir is discharged therefrom. A stationary contact member 80 is cated in the top of the pressure-generating chamber and an auxiliary contact member 82 is carried by the piston 64. A movable contact member 84; is arranged to move vertically through the opening 74 and 76 into engagement with the auxiliary contact member upwardly into engagement with the contact member 80 thereby to complete the circuit through the switch. When the movable contact member 84 is moved downwardly the piston 64 is also moved downwardly under urge of the springs 86, thereby separating the stationary and auxiliary contact members and drawing an arc therebetween. The downward movement of the movable contact 3 member is restricted by the abutments 88 on the piston-supporting rods 90. Further downward movement of the movable contact members 84 thus draws an are between it and the auxiliary contact member in the chamber l 68. The are is drawn out of the apertures 7 4 and 76 as the movable contact member passes out of these apertures. The are drawn between the main and auxiliary contact members 80 and 82 respectively generates a gaseous pressure in the chamber 66, which pressure acts upon the oil in the oil reservoir 70 through the parts 7 2. As a consequence the oil in the oil reservoir is forced downwardly and out of the aperture 76 in the bottom of the reservoir. By reason of the annular con struction of the discharge opening, the oil flows into the arc from all sides and constrains the are so that the arc is reduced in cross section and comes in intimate contact with the oil and thence is rapidly cooled and ratus. ,After the arc has been interrupted the gases are vented from the various chambers and reservoir and the chambers and reservoir are refilled with oil in the manner heretofore described. With the modification. above described, the arc gases that set up a pressure on the arc-extinguishing oil are kept separate from the gases of the are that isinterrupted, at least until interruption has been effected.

While in Figs. 1 and 4f, the oil is placed under a pressure by the action of one are and acts upon a second arc in series with the first arc, the two arcs are in effect essentially the same arc as .it is of no consequence so far as the operation is concerned whether the pressure for moving the oil is generated by one portion of an arc and the oil acts on another portion of the same arc, as in Fig. 3, or whether the portions are separated by an interposed conductor as in Figs. 1 and 4.

It will be noted that, in the examples of the invention above described, the oil is taken from, or is under the pressure of, a high pressure portion of the arc, and is directed into a low pressure portion of the arc. Hence the oil is under a positive pressure difference so that the discharged oil can be directed in an effective manner into the low pressure portion of the arc. In Fig. 1, for instance, the arcthat is within a chamber 38 (or is at a high pressure, since the arc gases are confined by thechamber. The are that is outside the chamber is under low pressure since, relatively speaking, it is not confined. The pressure of the oil in the chamber, that is effective in causing a flow of oil through the duct 54 (or is the difference between the pressure of the high and low pressure arcs. Since this difference is great, there is a positive pressure on the oil by which the oil can flow forcibly out of the vent of the duct and hence be directed in an effective mannerto act on the low pressure arc. The same is true with respect to the constructions illustrated in Figs. 3 and 4 I claim:

.1. An electric switch having the combination of two pressure-generating oil-containing chambers, means to establish two circuit-interrupting arcs that are in series with each other and are partly within and partly external of said chambers, and an oil-containing conduit of large capacity communicating with each chamber having an outlet directed against the external arc ofthe other chamber. i

2. An electricswitch having the combinas tion of twopressure generating chambers, means to establish two circuit-interrupting arcs that are in series with each other and are partlywithin and partly external of said chambers, and a conduit communicating with each chamber having an outlet directed again'stthe external arc of the other chamher, said chambers and conduits being under a body 01 and containing oil.

3. An electric switch having the combination of a pressure-generating chamber having an opening, means to draw a circuit-interrupting are within said chamber Where the arc is under high pressure and through and beyond said opening where the arc is under low pressure, and means including a liquid reservoir responsive to the high pressure within said chamber to force a stream of liquid against the low pressure arc that is external of the chamber and beyond said opening.

4. An electric switch having the combination of a pressure-generating chamber having a bottom wall provided with an opening, a liquid reservoir surrounding said chamber and having an opening in its bottom wall which is below said chamber-opening, means to draw a circuit-in'terrupting are within said chamber and through said openings, said reservoir having communication with the interior of said chamber and the pressure in said chamber forcing liquid from said reservoir against the arc and through the reservoir-opening and against the external arc.

5. An electric switch having two oil containing receptacles, means to establish an arc in one only and also outside of said receptacles so that the confined arc generates a pressure in its enclosing receptacle and the unconfined are outside the receptacles is free from pressure, means to subject the oil in the arc-free receptacle to pressure derived from the pressure in the arc-containing receptacle, and means to direct the pressure oil against the unconfined arc.

6. An electric switch having an oil-containing pot, a stationary contact member therein, a movable contact member movable into and out of said pot and into and out of contact with said stationary contact member and establishing an are that has a confined pressure-developing portion within said pot and a free pressure-free portion outside said pot, an oil containing receptacle located beyond the field of said arc, means for applying pressure on the oil in said receptacle from said pot, and means for directing said pressure oil against said free arc.

7. An electric switch havin two oil containing chambers, one succeeding the other and both having aligned openings in the bottoms thereof, a fixed contact member in the inner receptacle, a movable contact member movable into and out of said aligned openings into and out of engagement with said fixed contact member and arranged to establish an are that is partly within said inner chamber and partly without both chambers, means establishing pressure communication between the upper portions of said chambers so as to subject the oil in said outer chamber to pressure of the arc gases in said inner chamber, and means including the opening in said outer chamber to direct the pressure oil therein against the unconfined portion of the are without said chambers.

In testimony whereof, I have signed my name to this specification.

GEORGE A. BURNHAM. 

